SOL Route - Decentralized Encrypted File Marketplace - Oct 5 to Oct 18 2025 (Biweekly Week 10-11) - PLDG 4

[adielliot37]

SOL Route - Decentralized Encrypted File Marketplace - Oct 5 to Nov 22 2025 (Week 10-12 Bridged Cohort Week 1-2) - PLDG 4

Contributors

• @adielliot37

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Repo

https://github.com/adielliot37/SOL-Route

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SOL Route

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Accomplished Tasks - Week 1

• Built Node.js/TypeScript backend with Express RESTful API architecture for marketplace operations.
• Integrated Storacha/IPFS storage via MCP REST client using JSON-RPC 2.0 protocol for decentralized file hosting.
• Implemented MongoDB persistence with Mongoose schemas for Users, Listings, Orders, and KeyVault.
• Connected to Solana blockchain (Devnet) for cryptocurrency payments using Web3.js SDK.
• Built wallet authentication system with Ed25519 signature verification for user login.
• Created memo-based payment tracking: SPL Memo program links on-chain transactions to orders via UUID.
• Designed purchase flow: init order → generate payment transaction → verify on-chain → deliver content.
• Implemented seller dashboard endpoint showing listings with purchase history and transaction signatures.
• Added security middleware: Helmet for HTTP headers, CORS configuration, 50MB payload limit for base64 files.
• Built flexible MCP response parser handling multiple Storacha API formats (content array, text, direct object).

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Accomplished Tasks - Week 2

• Implemented AES-256-GCM file encryption on server-side before Storacha upload (plaintext never stored).
• Upgraded to AWS KMS integration for enterprise-grade master key management with HSM backing.
• Created KeyVault schema storing wrapped content keys with KMS key ID, version tracking, and Base64 encoding.
• Built client-side X25519 keypair generation with password-based encryption using PBKDF2 (310,000 iterations).
• Implemented ephemeral key exchange for forward secrecy: server generates fresh keypair per delivery.
• Designed atomic payment-for-key exchange: verify Solana transaction → unwrap from KMS → seal to buyer's pubkey → deliver.
• Built session management system with 1-hour key expiration and automatic cleanup on inactivity.
• Added password-protected private keys stored encrypted in browser localStorage (never sent to server).
• Created purchase check endpoint to prevent duplicate payments and enable re-download without re-payment.
• Implemented production cleanup: removed console.logs, unnecessary comments, emojis from codebase.

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Accomplished Tasks - Week 3 (New) (Bridged Cohort)

• Implemented client-side decryption flow: password prompt → unseal content key → AES-GCM decrypt → file download.
• Built Web Crypto API integration for AES-256-GCM decryption and PBKDF2 key derivation in browser.
• Integrated libsodium (sodium.js) for X25519 ECDH key exchange and crypto_box_open_easy sealed box decryption.
• Created password-based key encryption system: PBKDF2 derives AES key → encrypts X25519 private key → stores in localStorage.
• Implemented key recovery mechanism: user password → re-derive PBKDF2 key → decrypt private key → unseal content key.
• Added Solana wallet integration for transaction signing and memo-based payment submission.
• Built payment verification flow: transaction signature → on-chain memo lookup → server validation → key delivery.
• Created file obfuscation system: partial filename display (first 25% + last 25%) before purchase.
• Implemented automatic purchase detection: checks existing purchases to prevent duplicate payments.
• Added session expiry tracking: getTimeUntilExpiry() and refreshKeyExpiry() for 1-hour timeout management.

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Update

• Enhanced Security Architecture:

  • Multi-layer encryption: AES-256-GCM (files) + X25519 (key exchange) + PBKDF2 (password) + AWS KMS (master keys).
  • Forward secrecy: Ephemeral keypairs generated per transaction, deleted after delivery.
  • Zero-knowledge client: Private keys never leave browser, encrypted with user password.
  • Key isolation: Master key (AWS HSM) → Content key (per file) → User key (per buyer).
  • Authenticated encryption: AES-GCM auth tags prevent tampering, XSalsa20-Poly1305 for key delivery.

• Technical Implementation:

  • Seller encryption:

    • Generate random 256-bit content key
    • Encrypt file: AES-256-GCM with 96-bit IV, 128-bit auth tag
    • Wrap content key with AWS KMS encrypt
    • Upload encrypted file to Storacha (returns CID)
    • Store: CID + wrapped key + KMS key ID in MongoDB

  • Buyer keypair generation:

    • User password → PBKDF2 (310k iterations, SHA-256, 16-byte salt)
    • Generate X25519 keypair (Curve25519, 32-byte keys)
    • Encrypt private key: AES-256-GCM with password-derived key
    • Store encrypted private key + salt in localStorage
    • Send public key to server

  • Payment verification:

    • Solana transaction includes SPL Memo with order UUID
    • Server scans blockchain for memo match + exact lamport amount
    • Records transaction signature and block timestamp
    • Prevents double-delivery via order state machine

  • Key delivery (server):

    • AWS KMS decrypt to unwrap content key
    • Generate ephemeral X25519 keypair
    • ECDH: compute shared secret with buyer's public key
    • Encrypt content key: XSalsa20-Poly1305 (crypto_box_easy)
    • Return: sealed key (nonce + ciphertext) + ephemeral public key
    • Ephemeral private key deleted immediately

  • Decryption (client):

    • User password → PBKDF2 → decrypt private key from localStorage
    • Parse sealed key: extract 24-byte nonce + ciphertext
    • crypto_box_open_easy with private key + ephemeral public key
    • Recovered content key used for AES-256-GCM file decryption
    • File downloaded as Blob with original mime type

• What went well:

  • Complete end-to-end encrypted marketplace with production-grade security.
  • Forward secrecy: past transactions remain secure even if server compromised.
  • Password-only security: no complex key management UI, just password entry.
  • Session management limits exposure window (1-hour expiry on inactivity).
  • Atomic delivery: payment confirmation required before key release.
  • Re-download capability: purchased files accessible anytime with same password.
  • Clean separation: encrypted blobs on IPFS, wrapped keys in MongoDB, user keys in browser.

• Challenges:

  • Storacha MCP response format variations required flexible parsing.
  • Coordinating encryption across three key layers (KMS, content, user).
  • Solana transaction parsing: memo extraction + transfer validation.
  • Browser crypto API differences: Web Crypto vs libsodium integration.
  • Session state management: balancing security (expiry) vs UX (re-entry).
  • Large file handling: base64 encoding overhead for 50MB+ files.
  • Key recovery UX: ensuring users understand password is unrecoverable.

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Next Tasks

• Add file preview generation (thumbnails, metadata) before purchase.
• Implement rating/review system for sellers and content quality.
• Add multi-file bundle support for selling collections.
• Create WebSocket notifications for real-time payment confirmations.
• Migrate to Solana mainnet and production Storacha endpoints.
• Add content categorization and search functionality.
• Implement royalty/revenue sharing for content creators.
• Add hardware wallet support (Ledger, Trezor) for key storage.
• Implement key rotation mechanism for AWS KMS master keys.

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